Comparison of measured and modeled stratospheric BrO: Implications for the total amount of stratospheric bromine

Abstract

Stratospheric BrO was spectroscopically monitored by its UV absorption in direct sunlight on 8 balloon flights that were conducted at middle and high latitudes in 1996 through 2000 [e.g., Ferlemann et al., 1998, 2000]. For conditions where detailed photochemical model calculations (Chipperfield, 1999) correctly predict other measured chemical (e.g., NO2, O3) and dynamical (e.g. N2O, F12, et cetera) tracers, the total stratospheric bromine (organic and inorganic) amount (Bry) is inferred. An excellent agreement between measured and modeled stratospheric BrO is found, assuming JPL-97 kinetics and Bry=20 ppt in the photochemical model. As the BrO absorption cross section (σBrO) is the only external parameter used in the measurement, our finding tightly constrains the amount of total inorganic bromine (Briny), 20±2.5 ppt above 25 km in 1996/97, as well as the photochemistry of stratospheric bromine.